Delivery tube for irrigation and fertilization system and method for manufacturing same

ABSTRACT

The invention is directed generally to improvements in irrigation and fertilization assessment and delivery. More specifically, embodiments of the invention provide an improved fluid delivery tube, method to manufacture such tube, and systems that include such tube. The delivery tube is beneficial at least because it minimizes the life cycle cost of a plant-responsive delivery tube.

BACKGROUND

1. Field of the Invention

The invention relates generally to irrigation and fertilization systemsand methods, and more particularly, but without limitation, to animproved delivery tube that is locally responsive to plant hydration andnutrition needs.

2. Description of the Related Art

Agronomic practices include various irrigation and fertilizationassessment and delivery methods. Typically, growers measureenvironmental conditions (i.e. rainfall, soil moisture, pH, temperature,etc.) and/or observe plant development to determine an amount of waterand fertilizer to apply during a plant's growing season. Well-knownmethods also exist for providing the irrigation and fertilization; forinstance, sprinkler systems and drip lines are commonly utilized.

Conventional assessment methods and delivery systems have manyshortcomings, however. For example, assessment methods that rely on datameasurements and observations to estimate plant needs are reactive.Accordingly, such methods necessarily introduce a time delay between theassessment and the delivery of the water and fertilizer. Sufficientlylong delays can stress the target plants and/or decrease the value ofthe assessment (since the measured conditions may quickly change). Inaddition, such assessments often lack geographical precision, which maybe disadvantageous, for instance, where moisture conditions varysubstantially within a crop field due to changes in elevation or otherfactors.

Even if the needs assessment is correct, timely, and sufficientlyprecise, conventional irrigation and fertilization delivery systemsoften fail to provide the desired level of water and/or nutrients toeach plant. There are many reasons for this. For example, in anirrigation system, static water pressure can vary based on distance fromthe water source, field topography, and/or leaks or other componentfailure. Distributed controls that would overcome such systemlimitations, and also enable delivery of water and nutrients accordingto the demand of each plant, are generally cost prohibitive. As aresult, many delivery systems apply too little or too much water andnutrients. This decreases crop yield. The application of too much wateris a waste of a precious natural resource; the application of too muchfertilizer can harm the environment.

Given the importance of food supply, water management, and the need toprotect the environment, improvements in irrigation and fertilizationassessment and delivery methods are urgently needed.

SUMMARY OF THE INVENTION

Embodiments of the invention seek to overcome one or more of theaforementioned limitations with an improved delivery tube, method tomanufacture such tube, and systems that include such tube.

An embodiment of the invention provides a delivery tube that includes: asubstrate, at least a portion of the substrate being treated with ahydrophilic polymer; and a backer coupled to the substrate, the deliverytube being configured such that the substrate and the backer are eachdisposed along a functional length of the delivery tube. The tube islocally responsive to the irrigation and fertilization needs of adjacentplants.

Another embodiment of the invention provides a cost-effective method formanufacturing a delivery tube. The method includes: preparing ahydrophilic polymer solution; coating at least a portion of thesubstrate with the hydrophilic polymer solution to produce a responsiveweb; drying the responsive web; and welding the responsive web to thebacker to form a delivery web. The delivery web may be slit to formmultiple delivery tubes.

Another embodiment of the invention provides a system that includes adelivery tube and a pressure regulator. The pressure regulator iscoupled between a fluid source and the delivery tube.

A delivery tube that is locally responsive to plant needs is beneficialbecause it simplifies the needs assessment task, reduces the requirementfor distributed controls in the delivery system, improves plant yield,conserves scarce water and fertilizer, and respects the environment. Thecost-effective manufacturing method and high level of product durabilityminimize life cycle cost and encourage adoption.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the detaileddescription below and the accompanying drawings, wherein:

FIG. 1 is a schematic diagram of an irrigation and fertilization system,according to an embodiment of the invention;

FIG. 2 is a schematic diagram of an irrigation and fertilization system,according to an embodiment of the invention;

FIG. 3 is an assembly view of a delivery tube, illustrated incross-section, according to an embodiment of the invention;

FIG. 4 is a plan view of a delivery tube, according to an embodiment ofthe invention;

FIG. 5 is an end view of a partially-opened delivery tube, according toan embodiment of the invention;

FIG. 6 is an end view of a partially-opened delivery tube, according toan embodiment of the invention;

FIG. 7 is an end view of a partially-opened delivery tube, according toan embodiment of the invention;

FIG. 8 is an end view of a delivery tube, according to an embodiment ofthe invention;

FIG. 9 is a flow diagram of a method for manufacturing a delivery tube,according to an embodiment of the invention;

FIG. 10 is a schematic diagram of a coating apparatus, according to anembodiment of the invention;

FIG. 11 is a schematic diagram of a coating apparatus, according to anembodiment of the invention;

FIG. 12 is a schematic diagram of a coating apparatus, according to anembodiment of the invention;

FIG. 13 is a plan view of a delivery web subsequent to a welding step,according to an embodiment of the invention; and

FIG. 14 is a plan view of a three delivery tubes, according to anembodiment of the invention.

DETAILED DESCRIPTION

Embodiments of the invention will be described more fully with referenceto FIGS. 1 to 14, in which embodiments of the invention are shown. Thisinvention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein. Thesub-headings below are for organizational convenience only, and featuresof the invention may be described anywhere in this specification. In thedrawings, physical features are not necessarily rendered to scale. Whereidentical reference numbers are repeated, they refer to the same orsubstantially similar features.

Exemplary Systems

Embodiments of the invention can be used on farms of varying scale. FIG.1 is a schematic diagram of an irrigation and fertilization system,according to an embodiment of the invention. The embodiment illustratedin FIG. 1 might be applicable, for instance, to a family farm or othersmall plot. As shown therein, a small plot supply system 105 isconfigured to harvest rain water. The small plot supply system 105 feedsa header pipe 110 that is coupled to multiple delivery tubes 115 viafittings 125. Crops 120 are disposed adjacent to each of the deliverytubes 115.

The small plot supply system 105 includes roof gutters 130 positioned tocooperate with a roof 135. Downspouts 140 are coupled to the gutters 130at an input end and disposed over a storage tank 145 at an output end.The storage tank 145 could be or include, for instance, and elevatedplastic 55-gallon drum. The storage tank 145 is configured with a lid150 having a screen filter 155. The storage tank 145 further includes anoverflow outlet 160. An isolation valve 165 is disposed inline betweenthe storage tank 145 and a supply system output 170.

Preferably, each delivery tube 115 includes a responsive portion alongits length that is hydrophilic and configured to deliver water or anaqueous solution in response to surfactant root exudates from a rootsystem of the crops 120. In other words, each section of each deliverytube 115 is configured to efficiently deliver water or other solutionaccording to individual crop demand rather than at a regulated rateprovided, for example, by sprinkler and drip-based irrigation systems.

As used herein, the term “delivery tube” refers generally to a devicefor fluid conveyance along a length of the delivery tube and through atleast a portion of its walls, and is not intended to restrict thephysical form of such device to one having a circular cross-section. Forinstance, in embodiments of the invention the delivery tubes 115 are“tape-like” with a relatively flat cross-section when unfilled with afluid. Alternative configurations for the delivery tubes 115 aredescribed in more detail below with reference to FIGS. 3-8.

During periods of rain, the gutters 130 and downspouts 140 direct rainwater to the storage tank 145. The screen filter 155 filters solidparticles from the rain water as it enters the storage tank 145. Ifwater in the storage tank 145 exceeds a predetermined maximum waterlevel 157, excess water is discharged from the storage tank 145 via theoverflow outlet 160.

The size of storage tank 145 and the change in elevation between themaximum water level 157 and the supply system output 170 determine amaximum pressure provided by the small plot supply system 105. Inembodiments of the invention, the desired pressure at the supply systemoutput 170 is relatively low, for instance within the range of 0.5-2.1lb/in² (PSI), for compatibility with the delivery tubes 115. The desiredpressure at the supply system output 170 will vary accordingly to theparticular configuration of the delivery tubes 115, however.

The isolation valve 165 could be closed, for instance, during periods ofrain (when the crops 120 are unlikely to need hydration) or duringmaintenance of the downstream irrigation system. When the isolationvalve 165 is open, the header pipe 110 supplies rain water to pressurizethe delivery tubes 115. Once pressurized, the delivery tubes 115 supplythe filtered rain water to the crops 120 in response to the rootexudates.

Variations to the system illustrated in FIG. 1 and described above arepossible. For example, in alternative embodiments, the small plot supplysystem 105 may further include a well water feed and/or municipal waterfeed to supplement the rain-harvesting features in filling the storagetank 145. Such additional feed(s) could be activated, for example, by afloat valve in the storage tank 145. There could be more than onestorage tank 145 coupled to the supply system output 170. In addition,one of more filters could be placed in-line between the storage tank(s)145 and the supply system output 170 in addition to, or instead of, thescreen filter 155. In alternative embodiments, the small plot supplysystem 105 includes a fertilizer injection subsystem. End caps and flushvalves are not shown in FIG. 1 but are preferably coupled to the header110. Likewise, each of the delivery tubes 115 may be crimped or cappedat a terminal end; alternatively, multiple delivery tubes may be joinedby a footer and such footer may include end caps and/or a flush valve.

FIG. 2 is a schematic diagram of an irrigation and fertilization system,according to an embodiment of the invention. The embodiment illustratedin FIG. 2 might be applicable, for instance, to a large commercialfarming operation. As shown therein, a commercial grower supply system205 feeds a header pipe 110 that is coupled to multiple delivery tubes115 via fittings 125. Crops 120 are disposed adjacent to each of thedelivery tubes 115.

The commercial grower supply system 205 includes a well pump 210 coupledto a source line 213. A fertilizer reservoir 215 is also coupled to thesource line 213 via a pump 220 and metering valve 225. Each of multiplechemical injection tanks 230 are connected to the source line 213 via acorresponding metering valve 235. Filters 240, pressure regulator 245,and pressure meter 250 are disposed in series between the source line213 and a system supply output 255. The commercial grower supply system205 feeds a header pipe 110 that is coupled to multiple delivery tubes115 via fittings 125. Crops 120 are disposed adjacent to each of thedelivery tubes 115.

The pressure regulator 245 is configured to output a relativelylow-pressure regulated fluid flow, for instance for a setting within therange of 0.5-2.1 PSI, for compatibility with the delivery tubes 115. Anexemplary regulator 245 is the Model 102 diaphragm regulatormanufactured by Ziggity Systems, Inc. The desired pressure setting forsuch an adjustable pressure regulator will vary accordingly to theparticular configuration of the delivery tubes 115. In alternativeembodiments, other pressure settings and/or other regulators 245 couldbe used.

In operation, the commercial grower supply system 205 supplies filteredwater or a filtered aqueous solution including fertilizer and/orchemicals at a predetermined (and relatively low) pressure via a headerpipe 110 to delivery tubes 115. The pressurized delivery tubes 115supply the water or aqueous solution including soluble fertilizers inresponse to root exudates from the crops 120.

Variations to the system illustrated in FIG. 2 and described above arepossible. For example, in alternative embodiments, the commercial growersupply system 205 could include a municipal water feed to supplement thewater supply from the well pump 210. The commercial grower supply system205 may not include the chemical injection tanks 230 and associatedmetering valves 235. Moreover, the type and quantity of filters 240could vary, according to design choice. An isolation valve could beincluded, for instance between the pressure meter 250 and the supplysystem output 255. End caps and flush valves are not shown in FIG. 1 butare preferably coupled to the header 110. Likewise, each of the deliverytubes 115 may be crimped or capped at a terminal end; alternatively,multiple delivery tubes may be joined by a footer, and such footer mayinclude end caps and/or a flush valve.

Delivery Tubes

Alternative configurations of the delivery tubes 115 are described belowwith reference to FIGS. 3-8. FIG. 3 is an assembly view of a deliverytube, illustrated in cross-section, according to an embodiment of theinvention. As shown therein, an embodiment of the delivery tube 115 isgenerally an assembly of a responsive side 305 to a backing side 310.The responsive side 305, or at least a portion thereof, is responsive toroot exudates from a root system of the crops 120. The backing side 310is a supporting structure. In the embodiment illustrated in FIG. 3, theresulting delivery tube 115 is essentially a “tape-like” or “lay flat”structure when not in use. The tape-like format is advantageous becausethe delivery tube 115 can be compactly spooled (reeled) for storage anddistribution. The responsive side 305 includes a substrate that istreated with a hydrophilic polymer solution to make it responsive toroot exudates. The substrate preferably includes a nonwoven fabric ofpetroleum-based plastic polymers, for instance polyethylene (PE) orpolypropylene (PP).

Acceptable nonwoven PE fabrics for the responsive side 305 include, forinstance, DuPont Tyvek (1025BL, 1025D, 1053B, 1053D, 1056D, 1058D,1059B, 1073B, 1073D, 1079, 1079B, 1079D, or 1085D). Suitable nonwoven PPfabrics for the responsive side 305 include, for example, FibertexSpuntex 55, Hanes Imperial RB2, Mitsui Chemicals, Suzhou Mediceng (LB543or WH001F), and related products. Other PE and PP fabrics may also besuitable substrates, according to application demands.

Suitable hydrophilic polymers for treating the responsive side 305include various Polyhydroxystyrene (PHS) co-polymers, for example,Polyhydroxystyrene-Novolak (PHS-Novolak),Polyhydroxystyrene-Benzotriazole (PHS-BZT), and PolyhydroxystyreneHydroxyethyl Methacrylate (PHS-HEMA). Other hydrophilic polymers mayalso be used.

The backing side 310 may be or include, for example, MetallocenePolyethylene (PE) from Brentwood Plastics, Inc., Low-DensityPolyethylene (LDPE), Linear Low Density Polyethylene (LLDPE), Copolymerpolypropylene (PP) by Bloomer Plastics Inc. (BPI) (e.g., the “random”and “impact” products), Homopolymer polypropylene (PP) by BPI, andUrethane Film by Medco Coated Products (a division of Medco Labs). Thebacking side 310 material may have a thickness, for example, in therange of 2 to 15 mils.

Because the responsive side 305 requires additional processing with thehydrophilic solution, the responsive side 305 is more expensive tomanufacture than the backing side 310. The illustrated assembly is thusless expensive than a delivery tube formed entirely of responsivematerial. The backing side 310 also improves the durability of thedelivery tube 115 compared to a delivery tube that is formed entirely ofresponsive material.

Various configurations of the delivery tube 115 are described below withreference to FIGS. 4-8.

FIG. 4 is a plan view of a delivery tube, according to an embodiment ofthe invention. Weld areas 405 bond edges of the responsive side 305 tocorresponding edges of the backing side 310. The weld areas 405 providea fluidic seal to contain water or an aqueous solution in an interiorcavity of the delivery tube 115. The delivery tube 115 is intended forrelatively low pressure systems. Preferably, the seal formed by weldareas 405 should withstand a burst pressure of at least 4.0 PSI. In theillustrated embodiment, each weld area 405 includes three rows ofintermittent welds, the three rows being staggered with respect to eachother. Other weld patterns (intermittent or continuous) are possible.

FIG. 5 is an end view of a partially-opened delivery tube, according toan embodiment of the invention. In the illustrated embodiment, theresponsive side 305 may be saturated with a hydrophilic polymer solutionover the full width shown in cross-section. Lumen 505 is formed betweena portion of the responsive side 305 and a portion of the backing side310.

FIG. 6 is an end view of a partially-opened delivery tube, according toan embodiment of the invention. In the illustrated embodiment, thehydrophilic polymer is disposed on a coated portion 615 of an outersurface of the substrate 605. Uncoated portions 610 of the substrate 605extend into the weld areas 405. In one respect, the configuration shownin FIG. 6 may be advantageous because uncoated portions 610 of thesubstrate 605 may result in stronger weld areas 405. Selective patterncoating on a surface of the substrate 605 also reduces manufacturingcost relative to saturation coating at least because less hydrophilicpolymer may be required. Lumen 505 is formed between a portion of thesubstrate 605 and a portion of the backing side 310.

FIG. 7 is an end view of a partially-opened delivery tube, according toan embodiment of the invention. In the illustrated embodiment, thehydrophilic polymer is disposed on a coated portion 715 of an innersurface of the substrate 705. Uncoated portions 710 of the substrateextend into the weld areas 405. The configuration shown in FIG. 7 mayalso be advantageous because uncoated portions 710 of the substrate 705may result in stronger weld areas 405. Selective pattern coating on asurface of the substrate 705 also reduces manufacturing cost relative tosaturation coating at least because less hydrophilic polymer may berequired. Lumen 505 is formed between a portion of the substrate 705 anda portion of the backing side 310.

FIG. 8 is an end view of a delivery tube, according to an embodiment ofthe invention. As shown therein, a delivery tube with a circularcross-section includes a substrate 805 connected to a backing 810 atoverlap welds 815. In the illustrated embodiment, the substrate 805forms less than 50% of the delivery tube. The substrate 805 includes acoated portion 825 and uncoated portions 820. The coated portion 825represents hydrophilic polymer disposed on an outer surface of thesubstrate 805. The uncoated portions 820 extend into the overlap weldareas 815. The ratio between the substrate 805 and the backing 810 couldbe varied according to design choice. Decreasing the size of the coatedportion 825 and/or the dry polymer weight applied to the coated portion825 decreases the amount of water or fertilizer solution that isreleased at a given pressure. Lumen 505 is formed between a portion ofthe substrate 805 and a portion of the backing side 310.

Manufacturing Method

A manufacturing process for the delivery tube 115 is described withreference to FIGS. 9-14.

FIG. 9 is a flow diagram of a method for manufacturing a delivery tube,according to an embodiment of the invention. As shown therein, theprocess begins in step 905 and then prepares a hydrophilic polymersolution in step 910. Step 910 may include, for instance mixing a dryhydrophilic polymer powder with a solvent such as Isopropanol 99% (IPA).The concentration of hydrophilic polymer in the solution may be based,for instance, on the target substrate material, the desiredconcentration of dry hydrophilic polymer on the substrate, and thecoating method used. Suitable concentrations of hydrophilic polymer inthe solution may be in the range of 2.0-89.0 weight/volume percent, andare preferably in excess of 20 wt/vol % to facilitate high-speed coatingmethods which reduce evaporation and minimize production costs.

In step 915, the process coats a substrate (or portion thereof) with thehydrophilic polymer solution to produce a responsive web. As usedherein, a “coating” step could be a surface treatment, saturation, orother application of the hydrophilic polymer solution to the nonwovensubstrate material. The process dries the responsive web in step 920.The desired concentration of dry hydrophilic polymer on the substratewill vary according to the substrate material and other factors. As anexample, polymer weights in the range of 1.5-5.3 g/m² (gsm) haveproduced acceptable results with Tyvek PE substrates.

Next, the process welds the responsive web to a backing film to form adelivery web in step 925. Welding step 925 could be or include, forexample, rotary heat sealing, contact welding, ultrasonic welding, orother plastic welding method. The delivery web is then rolled (spooled)in step 930.

Preferably, steps 915-930 produce a multi-paneled delivery web. In thisinstance, the process slits the delivery web to form multiple deliverytubes in step 935 and then rewinds each of the multiple delivery tubesin step 940 before terminating in step 945. FIGS. 13 and 14 illustratean exemplary multi-paneled delivery web. Slitting step 935 may utilize,for example, one or more razors, one or more pairs of opposing circularknives, or a slit weld. Rewind step 940 may include rewinding each ofthe manufactured delivery tubes onto a reel at a desired speed andcapacity.

Variations to the manufacturing method described above with reference toFIG. 9 are possible. For instance, rolling step 930 may not be requiredfor a continuous manufacturing flow. Slitting step 935 and rewind step940 may be, and preferably are, combined into a single process step. Inaddition, where steps 915-925 produce a single-tube-width web ratherthan a multi-paneled web, steps 935 and 940 are not required at all.Exemplary coating methods for step 915 are presented below withreference to FIGS. 10-12, although other coating methods could be usedin the alternative.

FIG. 10 is a schematic diagram of a coating apparatus, according to anembodiment of the invention. As illustrated, the coating apparatus isconfigured so that a substrate web 1005 can move in a direction 1010 incooperation with pulleys 1025 and a Mayer rod (a/k/a a rod doctor) 1030.A coating pan 1015 contains a hydrophilic polymer solution 1020. Inoperation, the substrate web 1005 is dip coated with the hydrophilicsolution 1020. The Mayer rod 1030 operates to remove excess hydrophilicsolution 1020 after the substrate web 1005 has exited the coating pan1015.

Variations to the dip-coating apparatus illustrated in FIG. 10 arepossible. For instance the number and placement of the rollers 1025 canvary according to design choice. In addition, the use of a Mayer rod1030 is optional.

FIG. 11 is a schematic diagram of a coating apparatus, according to anembodiment of the invention. As shown therein, the coating apparatus isconfigured so that a substrate web 1105 can advance in a direction 1110in cooperation with pulleys 1125, steel roller 1130 and rubber roller1135. A coating pan 1115 contains a hydrophilic polymer solution 1120and is at least partially covered by a lid 1140. In operation, thesubstrate web 1110 passes through openings 1145 and 1150 in the lid 1140and is dip coated with the hydrophilic solution 1120. The lid 1140advantageously limits evaporation of solvent in the hydrophilic solution1120. The rubber roller cooperates with the steel roller 1130 to removeexcess hydrophilic solution 1120 after the substrate web 1105 has exitedthe coating pan 1115.

Variations to the configuration of the dip-coating apparatus illustratedin FIG. 11 are possible. For instance the number and placement of therollers 1125 can vary according to design choice. In addition, the useof a rubber roller 1135 is optional.

FIG. 12 is a schematic diagram of a coating apparatus, according to anembodiment of the invention. The coating apparatus is configured so thata substrate web 1205 can progress in a direction 1210 between opposingrollers 1225 and 1230. The roller 1225 is a gravure roller having anengraved (or etched) surface. The gravure roller 1225 is partiallysubmerged in hydrophilic polymer solution 1220 that is contained by thecoating pan 1215. Roller 1230 is a pressure roller configured to place adownward force on the substrate web 1205. A scraper (doctor) blade isdisposed adjacent to the gravure roller 1225. In operation, the gravureroller 1225 picks up hydrophilic polymer solution 1220 in its engraved(or etched) surface. The scraper blade 12235 removes excess hydrophilicpolymer solution 1220 from a surface of the gravure roller 1225.Remaining hydrophilic polymer solution 1220 is deposited from theengraved (or etched) cavities of the gravure roller 1225 to at least aportion of a surface of the substrate web 1205.

FIG. 13 is a plan view of a delivery web subsequent to a welding step,according to an embodiment of the invention. FIG. 13 illustrates adelivery web 1305, for instance, after the welding step 925 describedabove with reference to FIG. 9. In the embodiment shown in FIG. 13 thedelivery web 1305 includes six linear weld areas 1310, each of the weldareas 1310 including three staggered rows of intermittent welds. Theweld patterns in each of the weld areas 1310 could vary from what isshown.

FIG. 14 is a plan view of a three delivery tubes, according to anembodiment of the invention. FIG. 14 illustrates the delivery web 1305,for instance, after the slitting step 935 described above with referenceto FIG. 9. As shown, slit lines 1405 and 1410 separate the delivery web1305 into three delivery tubes 1415, 1420, and 1425.

Although FIGS. 13 and 14 illustrate a 3-panel approach, a manufacturingprocess that is configured for a greater or lesser numbers of panels isalso possible.

EXAMPLES

Preferably, delivery tubes are fabricated with a PE substrate and PEbacking, or with a PP substrate and a PP backing. Example delivery tubeshave been fabricated consistent with the configuration illustrated inFIGS. 3-5. A first group of samples used Tyvek 1059B PE substrates witha basis weight of 64.4 gsm and a thickness range of 2.9 to 10.1 mils. Asecond group of samples used Tyvek 1073 PE substrates with a basisweight of 74.6 gsm and a thickness range of 3.5 to 11.1 mils. Samplesfrom both groups were coated using a gravure coating process to apply adry hydrophilic polymer coating at a weight of 5.0 to 5.3 gsm. Thecoated PE substrates were bonded to a 5.0 mil thick Metallocene PEbacker via ultrasonic weld or rotary heat seal. The resulting deliverytubes had an internal diameter of ⅝ to ⅞ inches. In agriculturaltesting, the tubes were observed to be structurally robust and locallyresponsive to plant hydration and nutrition needs.

Summary

This specification has thus described an improved irrigation andfertilization delivery tube, a method for manufacturing the deliverytube, and exemplary systems utilizing the delivery tube. As describedabove, embodiments of the invention utilize low-cost materials andhigh-throughput manufacturing processes to produce a responsive deliverytube. The result is a delivery tube that can be sold at an affordableend-user price. The disclosed delivery tube is also highly durable inuse. Embodiments of the invention thus enable a highly-efficientplant-responsive irrigation and fertilization delivery system that iscomparable in total life cycle cost to less-efficient non-responsivedrip irrigation systems. This will benefit both small-plot andcommercial farms.

It will be apparent to those skilled in the art that modifications andvariations can be made to the tube, its manufacturing method, and/or itsuse in a system without deviating from the spirit or scope of theinvention disclosed herein.

We claim:
 1. A delivery tube, comprising: a substrate, a portion of thesubstrate being treated with a hydrophilic polymer; a backer coupled tothe substrate, the delivery tube being configured such that thesubstrate and the backer are each disposed along a functional length ofthe delivery tube, a lumen of the delivery tube being formed between atleast a portion of the substrate and at least a portion of the backer,wherein the substrate is connected to the backer at a first weld areaand a second weld area, the first and second weld areas extending overthe functional length of the delivery tube; and wherein the portion ofthe substrate being treated with the hydrophilic polymer excludes thefirst and second weld areas.
 2. The delivery tube of claim 1, whereinthe substrate includes a nonwoven polyethylene (PE) fabric and thebacker includes PE.
 3. The delivery tube of claim 2 wherein thesubstrate includes spunbond polyethylene.
 4. The delivery tube of claim2 wherein the backer includes at least one of Metallocene polyethylene(PE), low-density polyethylene (LDPE), and linear low densitypolyethylene (LLDPE).
 5. The delivery tube of claim 1, wherein thesubstrate includes a nonwoven polypropylene (PP) fabric and the backerincludes PP.
 6. The delivery tube of claim 1, wherein the hydrophilicpolymer includes a polyhydroxystyrene (PHS) co-polymer.
 7. A method formanufacturing the delivery tube of claim 1, the method comprising:preparing a hydrophilic polymer solution; coating at least a portion ofthe substrate with the hydrophilic polymer solution to produce aresponsive web; drying the responsive web; and welding the responsiveweb to the backer to form a delivery web.
 8. The method of claim 7wherein the preparing includes mixing a dry hydrophilic powder with asolvent.
 9. The method of claim 7 wherein the coating is performed usinga gravure coating apparatus.
 10. The method of claim 7 wherein thecoating is performed using a dip coating apparatus.
 11. The method ofclaim 10 wherein the dip coating apparatus includes a Mayer rod, theMayer rod configured to remove excess amounts of the hydrophilic polymersolution from the substrate.
 12. The method of claim 10 wherein the dipcoating apparatus includes: a pan configured to contain the hydrophilicpolymer solution; and a lid coupled to the pan, the lid configured tocover at least a portion of the pan, the dip coating apparatus thusconfigured to limit evaporation of solvent from the hydrophilic polymersolution during the coating.
 13. The method of claim 7 wherein thewelding joins portions of the substrate untreated with the hydrophilicpolymer to the backer.
 14. The method of claim 7 further includingslitting the delivery web to form multiple delivery tubes.
 15. A systemincluding the delivery tube of claim 1, the system comprising a pressureregulator coupled between a fluid source and the delivery tube.
 16. Thesystem of claim 15 wherein the pressure regulator is a diaphragmregulator.
 17. The system of claim 15 wherein the pressure regulator isconfigured to maintain a pressure output in the range of 0.5 to 2.1 PSI.18. The delivery tube of claim 1 wherein the backer includes urethanefilm.
 19. The delivery tube of claim 1, wherein the portion of thesubstrate being treated with the hydrophilic polymer is on an outersurface of the substrate.
 20. The delivery tube of claim 1, wherein theportion of the substrate being treated with the hydrophilic polymer ison an inner surface of the substrate.
 21. The delivery tube of claim 1,wherein the substrate forms less than 50 percent of an outer surfacearea of the delivery tube and the backer forms greater than 50 percentof the outer surface area of the delivery tube.